fix logic of register_default_spec
update check to default to new format on any implementation but cruby
move detection of new format for gem paths into defaults and a separate method
add simple test for default_gems_use_full_paths
Merge pull request #611 from jaggederest/fix_register_default_spec

Fix logic of register_default_spec

Issue #611 is needed for #612 which will sort the files list for packagers.

By fixing the issue now this method should not need to change as much.